From: mark salmon (masalmon@xxxxxxxxx)
Date: Wed Sep 13 2000 - 23:34:44 GMT-3
Comments in line
Kinton Connelly wrote:
> Which part are you disagreeing with? The part about static routes usually
> NOT being allowed? I don't know what to say except that everything I've
> read has indicated that unless you're specifically asked to put in a static
> route, they're usually not allowed.
I have never experienced what you indicated before toniht (as far as
IGRP adding a static route to an actual interface address). Unusually
the next hop is not the router it self (exception BGP) I saw it
myself. I will explore it before commenting further.
>
> But maybe you were talking about my statement about how a static route will
> be automatically generated if the default network isn't already in your
> routing table. You're right, I had the spirit of the situation but the
> details were a little shabby. :-) My apologies. I should have said:
Apparently only IGRP does this. Specifically I was talking about EIGRP
with this thread. If I was interested in reachability within a
IGRP/Classless network, I would redistribute using an identical mask
from the classful into the classless (IGRP) network so reachability is
achieved. Depending on the classless protocol, a STATIC (there it is)
router will be generated automatically pointing to the null interface.
I hope that this is acceptable by the lab folks as it does not point to
an actual interface but a "bit bucket"
>
> "A static route will be generated if the default-network specified doesn't
> lie along classful boundaries".
>
Does anyone know why this occurs?
> But now go to R2 and check your routing table. You still won't have a
> default route. Why? Because: (this is an important thing to understand
> about IGRP):
>
> IGRP won't advertise a network as a default route unless it can see that
> network in its routing table.
I believe that this is the same for EIGRP
>
> Look at your routing table - no 192.168.x.x networks anywhere. To take care
> of this, redistribute between OSPF and IGRP.
>
Or add it in the IGRP routing process on the router which has it
configured on an interface.
> As for my comments about the use of distribute-lists, that's just a
> practice I got into. They just keep things clean for me. There is probably
> a good technical reason or two for doing it this way, but my brain is
> already maxxed out on this OSPF/IGRP stuff - I'll leave it to the other
> group members to debate the use of distribute-lists.
I think it is good practice. In a non redundant network it is not
necessary (as long as split horizon is enabled)
>
> One more thing (I just re-read this statement):
>
> >True IP default network is a good way to achieve reachability from IGRP
> >domains to OSPF (or other classless networks), however, it is mutually
> >exclusive with mutual redistribution. In other words, as the goal of
> >redistribution is reachability, if one uses ip default network, it makes
> >mutual redistribution moot and vice versa.
>
> I disagree here. In my example above, you use "ip default-network" to set
> the default-network/route and you use redistribution so that R2 can see the
> network that's being tagged as the default. Without one or the other, I
> don't think you can get the above scenario to work.
Not necessary if the network (I would recommend using a class c ip as
long as the interfaces are /24). It is trickier if you are using class
A/B addresses. In those cases I think ip default network is a bad idea
if there are subnets in the classfull addresses already configured int
he IGRP domain.
Mark Salmon
Cisco Systems Inc
Phone:773-695-8235
Pager:800-365-4578
email: masalmon@cisco.com
Empowering The Internet Generation.
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 08:24:55 GMT-3